net: macb: fix uninitialized rx_fs_lock

[ Upstream commit 34b11cc56e4369bc08b1f4c4a04222d75ed596ce ]

If hardware doesn't support RX Flow Filters, rx_fs_lock spinlock is not
initialized leading to the following assertion splat triggerable via
set_rxnfc callback.

INFO: trying to register non-static key.
The code is fine but needs lockdep annotation, or maybe
you didn't initialize this object before use?
turning off the locking correctness validator.
CPU: 1 PID: 949 Comm: syz.0.6 Not tainted 6.1.164+ #113
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x8d/0xba lib/dump_stack.c:106
 assign_lock_key kernel/locking/lockdep.c:974 [inline]
 register_lock_class+0x141b/0x17f0 kernel/locking/lockdep.c:1287
 __lock_acquire+0x74f/0x6c40 kernel/locking/lockdep.c:4928
 lock_acquire kernel/locking/lockdep.c:5662 [inline]
 lock_acquire+0x190/0x4b0 kernel/locking/lockdep.c:5627
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x33/0x50 kernel/locking/spinlock.c:162
 gem_del_flow_filter drivers/net/ethernet/cadence/macb_main.c:3562 [inline]
 gem_set_rxnfc+0x533/0xac0 drivers/net/ethernet/cadence/macb_main.c:3667
 ethtool_set_rxnfc+0x18c/0x280 net/ethtool/ioctl.c:961
 __dev_ethtool net/ethtool/ioctl.c:2956 [inline]
 dev_ethtool+0x229c/0x6290 net/ethtool/ioctl.c:3095
 dev_ioctl+0x637/0x1070 net/core/dev_ioctl.c:510
 sock_do_ioctl+0x20d/0x2c0 net/socket.c:1215
 sock_ioctl+0x577/0x6d0 net/socket.c:1320
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x18c/0x210 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x35/0x80 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

A more straightforward solution would be to always initialize rx_fs_lock,
just like rx_fs_list.  However, in this case the driver set_rxnfc callback
would return with a rather confusing error code, e.g. -EINVAL.  So deny
set_rxnfc attempts directly if the RX filtering feature is not supported
by hardware.

Fixes: ae8223d ("net: macb: Added support for RX filtering")
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Link: https://patch.msgid.link/20260316103826.74506-2-pchelkin@ispras.ru
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: pchelkin91

drivers/net/ethernet/cadence/macb_main.c

@@ -4013,6 +4013,9 @@ static int gem_set_rxnfc(struct net_device *netdev, struct ethtool_rxnfc *cmd)
 	struct macb *bp = netdev_priv(netdev);
 	int ret;
 
+	if (!(netdev->hw_features & NETIF_F_NTUPLE))
+		return -EOPNOTSUPP;
+
 	switch (cmd->cmd) {
 	case ETHTOOL_SRXCLSRLINS:
 		if ((cmd->fs.location >= bp->max_tuples)